I got a first look at GP 9.0 this week via a partner webinar. It looks like another very solid upgrade similar to 8.0. The themes seem to be improved infrastructure, fixes for nagging issues and an overall Microsoftization of the product. That's a good thing in my opinion.
For example, installation is expected to be easier with 9.0. DynamicsGP 9.0 is installed using Microsoft's .MSP installtion files, not .exe's. This means that the installation will be more in line with other MS products and will allow for automatically updating client installations via Automatic Client Updates feature.
Also, batches close on save automatically now, AP check selection is improved, true check per address functionality has been added to AP and more features are included in the core.
I suspect there will be some pain with this release however. With Business Portal included you are looking at possibly an entirely new infrastructure (ASP.net 2.0, SQL Server 2005) underneath GP not to mention all the variations companies could be running. The product looks and behaves more and more like a Microsoft app and I think that this a good direction for GP. I'm looking forward to the upgrade.